Events on Friday, April 11th, 2014

Abstract: I will suppose that there is new physics above the TeV scale that is sequestered from the Standard Model in a hidden sector. One may want to invoke such a scenario to develop a viable model of dark matter, to motivate Z’ searches at colliders, or to ameliorate electroweak baryogenesis. It has not been generally recognized that if the hidden sector contains a spontaneously broken Abelian gauge symmetry, then our universe is permeated by a network of cosmic “dark strings.” With a mass scale of, say, 10 TeV these strings are far too light to be exposed by the standard gravitational probes. However, with a coupling to the (comparatively light) Standard Model fields, the strings can produce SM particles in abundance, and their decay products may be observed on Earth. Over the recent years, there has been significant success in constraining empirical models of cosmic strings via astrophysical probes, particularly the diffuse gamma ray flux measured by EGRET and Fermi-LAT. In this talk, I will focus on a simple model that allows only two points of interaction with the SM: the so-called gauge kinetic mixing and the Higgs portal, which have been probed up to the TeV scale by a variety of terrestrial tests. I will discuss whether bounds on the diffuse gamma ray flux that originates from cosmic dark strings provides a complimentary test at or above the TeV scale.

Abstract: The dynamo, a conversion of kinetic energy into magnetic energy in planets and stars is a fascinating puzzle, full of surprises. I will review some progress (and many more questions!) after over 15 years of lab experiments using liquid metals.